1. Field of the Invention
The invention relates to a color comparison device which can be used as a unified color language standard based an standard gray to identify the color depth, where a color is precisely identified by three attributes: hue angle, chroma and depth.
2. Prior Art
The fact that there is a lack of a common language and a lack of a standardized color scale in the communication of color among color related industries has impeded color conveyance and created difficulties in advancing the state of the art in industry. In order to overcome this problem, especially seeing that today's information age demands information be exchanged rapidly and accurately, there is a pressing need for the development of a unified color language for use by industry and by academia, in research and education, so to increase the competitiveness of products and promote the advancement of the state of the art in industry.
In the field of chromatics, color systems are composed of hue, chroma and value. As shown in FIG. 8A, a 3-dimensional color system includes hue sheets, where each hue sheet (HS) is centered on a colorless value axis (VA). This color solid has a non-color value axis (VA) at its center with lighter values at the top and darker values on the bottom. Of all values, white (W) is the lightest and black (B) is the darkest. Also, chroma (C) extends radially outward from the non-color axis (VA) as shown in FIG. 8B. How to standardize and communicate color has long been a goal that colorists have strived to attain. Even though each country in the world has researched its own type of color solid and color language, no single one has been widely accepted by the color industry. From this it can be seen that a color language and a color solid have yet to be developed in an ideal form.
The basic colors of the Munsell notation system, shown in FIGS. 9A and 9B, are red (R), yellow (Y), green (G), blue (B), purple (P). With the colors yellow-red (YR), yellow-green (YG), blue-green (BG), blue-purple (BP) and red-purple (RP) making the basic major hues. As shown in FIG. 9B, their value are indicated by eleven stages, No. 0, No. 1, No. 2, No. 3 . . . No. 10, with black (BL) being No. 0, white (W) No. 10 and nine stages of gray in between. The method of representing chroma was to set the non-color at 0 and represent the stages of hue increase by the numbers 1, 2, 3 . . . .The highest chroma for each pure color differs at each stage, according to the different hues. Red (R) has the most stages with 14. Therefore, the Munsell notation system is complex due to its chroma stages (FIG. 9A).
FIG. 10 represents the Ostwald notation system. As shown in FIG. 10B, the system contains 8 determinant colors: yellow (Y), orange (O), red (R), purple (P), blue (UB), blue-green (T), green (SG), and yellow-green (LG). Each type of color of the eight types of primary hues is divided into 24 hues. For instance, with the hue yellow, the standard yellow primary hue is placed at the center with different hues indicated on its left and right, making a total of three hues. The symbols 1Y, 2Y and 3Y are added with 2Y representing the primary hue. The other hues are indicated in an identical manner. As seen in the color solid, shown in FIG. 10A, the Ostwald notation system is a very useful notation system for matching colors, but the shortcoming in this type of arrangement is that its value stages are not well ordered.
In FIG. 11, one can see the practical color coordinate system (P.C.C.S.) developed by the Japanese Color Research Institute. The special characteristic of this notation system is that it provides an appropriate combination of color matching sheets and also makes use of the strengths of the Munsell notation system and Ostwald notation system. Each hue has its own number and all the colors have the same kind of numbering. According to the P.C.C.S. differentiation method, red containing purple (PR) is the first of the hue numbers; number two is red (R); number three is red containing yellow; number four is orange containing red (RO). By passing through the hues yellow (Y), green (G), blue (B), purple (P), and red-purple (RP) once in the circle, red-purple becomes the hue number twenty-four and then advances to red (R).
In addition, there exist numerous different color theories on which the current international systems are based; however, they are all identical with respect to that they all use the three level structure of hue, chroma and value.